The conventional pendant type automatic sprinkler head includes a body or frame that has an outlet which is normally enclosed by a valve cap and the cap is held in the closed position by a releasable lever assembly which includes a low melting point fusible element. With a pendant-type sprinkler head, the lever assembly extends downwardly beneath the ceiling of the building, and when the temperature increases to a predetermined level, the fusible element will melt, releasing the lever assembly to open the outlet and discharge the water.
In residential dwellings and commercial buildings, it is often desired to utilize a sprinkler head that is located above the ceiling, so that the operative parts are not exposed to view. With this type of construction, the sprinkler head is concealed within the ceiling by a decorative plate that is mounted flush against the undersurface of the ceiling, so that the operative parts are not visible. U.S. Pat. Nos. 3,633,676, 3,714,898 and 4,015,665 describe concealed sprinkler heads.
The conventional concealed sprinkler had includes a cylindrical sleeve or cup, which is secured around the cast metal frame or body. In the final assembly, and after testing of the sprinkler head for possible leaks, a decorative cover plate is attached to the sleeve and encloses the sprinkler head as well as the opening in the ceiling. In normal practice, the sleeve is preassembled in the factory with the frame. At the location of use, the sprinkler head, along with the attached sleeve, is installed with the water pipe line and after installation, the sprinkler head is tested for possible leakage. Because of the presence of the cylindrical sleeve, small leakage at the threaded joint may not be readily visible, with the result that the time required for the pressure testing procedure is substantially increased.
In order to properly position the cover plate of the concealed sprinkler head with respect to a suspended ceiling, the body or frame of the sprinkler head must be installed a precise distance from the lower surface of the ceiling. Concealed sprinkler heads, as used in the past, have had minimum provisions for adjustment, with the result that if the critical distance between the body and the ceiling is not maintained, the cover plate would not be positioned flush with the ceiling, thereby resulting in an unsightly gap.